The patent focuses on the attachment between the adjusting screw and its supporting ferrule. The adjusting screw is held in place by the supporting shoulders on the ferrule, and the spring-loaded pivot pin. Many examples marked "Robinson Patent June 16, 1885" in an oval border. A 12-inch example marked P.S.&W. (Peck, Stow & Wilcox) WARRANTED with the patent date is also known. Peck, Stow & Wilcox was advertising Robinson's Patent Steel Bar Wrench in 1894.

The ferule with supports on both side of the "rosette" is the subject of Robinson's May 27, 1884 patent (no. 299,165).